After a couple of hours the screen goes black. Sound is still on

The problem does depend on what you see with the LEDs.. Also if you hear the high voltage drop out (hear static discharging just after screen goes black).. If the led just keeps flashing 5 times over and over, then you have an AKB error, most common, and caused by aging picture tubes. This means the set is getting old but you can adjust them up a bit to temporarily solve the issue.. see the led blinks.. sony has the best self diagnostic function in the industry =

Diagnosis Items and Prediction of Malfunction Location
• When a malfunction occurs the TIMER/STAND BY indicator only blinks for one of the following diagnosis items. In case of
two or more malfunctions, the item which first occurred blinks. If the malfunctions occurred simultaneously, the item with the
lower blink count blinks first.
• The screen display displays the results regarding all the diagnosis items listed below. The display “ 0 ” means that no malfunctions
occurred.

2: OCP Low B and +B line detect DET SHORT, and shut-down POWER ON RELAY.
Reset by turning power on/off.
In case of +B is loaded approx. 1.5A or more, microcomputer detects it via IC6102.
3: OVP In case of +B becomes approx. 150V or more, POWER ON RELAY shuts down and microcomputer detects it via IC6102.
Reset by turning power on/off just the same as OCP.
4: V Stop In case of V Drive disappeared, Q5005 detecs it and shut-down POWER ON RELAY. Microcomputer detects it and makes LED
blinking.
5: AKB IK detection. Makes LED blinking in case of microcomputer doesn’t detect IK returns of IC511 (CXA2101AQ) 30 seconds or
more.
6: H Stop In case of H DRIVE is disappeared, Q5006 detects it and shut-down POWER ON RELAY shuts down.
Microcomputer receives H Stop data from Q5006 and makes LED blinking.
7: HV Stop In case of HV becomes 33KV or more. IC8006 and IC8010 detect it and shut-down
POWER ON RELAY. Microcomputer makes LED blinking.
8: Audio In case of DC component overlaps the output of Audio Amp., POWER ON RELAY shuts down.
Microcomputer detects it and makes LED blinking.

Hi and welcome to FixYa,

Either the lamp or heat related issue. In most cases, there is a thermal sensor that triggers auto shutdown if the temp internally exceeds a threshold. In some cases, dirt particularly dust affects the reaction time of the thermal sensor switch. In some instances, it could be a dried up or cold solder connection or even a loose connection.

This of course would require opening the unit, perform voltage measurements,determine faulty component and subsequent part(s) replacement. Further, a fair familiarity of electronic components/circuitry and safety procedures, use of a DVM and a soldering iron would be required. It would be to your added advantage access to a service manual or at the very least a schematic diagram with voltage readings.Should you be uncomfortable performing a DIY (do-it-yourself), perhaps your best bet would then be to seek the services of a qualified professional.

Good luck and Thank you for using FixYa.

If you have access to the circuit board... buy a small can of compressed air. turn on the tv ... when it stops working blow air onto sections of the board till it goes back on. once you have narrowed down the area... you concentrate on specific parts to find the part over heating. that's the part you replace... or have someone replace for you. P.S i would start in the power supply area.

Hi,
Do the leds blink?

the problem is most likely the lamp, it maybe near its end or overheating.

you'r not alone with the problem.
http://www.fixya.com/support/t420876-sony_kdf_46e2000_screen_goes_blank